The invention relates to thermoplastic molding compositions comprising styrene copolymers and comprising polyamides, to processes for their production, and to their use, and also to moldings, fibers, and foils produced therefrom.
Polymeric blends composed of styrene copolymers and of polyamides are known per se. Binary blends composed of polyamides and of styrene copolymers have very poor toughness values, due to the incompatibility of polyamide with, for example, styrene-acrylonitrile polymer. The toughness of blends can be raised significantly by using functionalized styrene-acrylonitrile copolymers (SAN copolymers). Products of this type moreover have interesting properties such as high impact resistance, and good flowability, and chemicals resistance. Particularly suitable compatibilizers are styrene-acrylonitrile-maleic anhydride terpolymers, styrene-N-phenylmaleimide-maleic anhydride terpolymers, and methyl methacrylate-maleic anhydride copolymers. It is assumed that the amino or carboxy end groups of the polyamides react with the functional groups of the co- and terpolymers mentioned, with in-situ production of copolymers which bring about the compatibility between the styrene copolymer phase and the polyamide phase. Polymer mixtures of this type with a modified interface are generally termed polymer alloys.
The styrene copolymer-polyamide blends known hitherto have insufficient UV resistance for many applications. Weathering resistance can by way of example be improved by use of impact modifiers which have no olefinic double bonds. The use of these can lead not only to higher materials costs but also to a significant reduction in notched impact resistance at low temperatures. Another possibility is to use polyamides having sterically hindered piperidine end groups as HALS stabilizers. However, when processing conditions are unfavorable, use of, for example, molding compositions comprising triacetonediamine (TAD) leads to a reduction in fracture energy at low temperatures.
WO 2005/040281 discloses thermoplastic molding compositions which comprise polyamide having TAD end groups, styrene-acrylonitrile-maleic anhydride terpolymers, graft rubbers, and, frequently, phthalic anhydride. The property profile of the molding compositions described is not ideal for all applications.